Effect of cognitive load on postural control.

The present study reports findings from two experiments on the relation between a mental task (silent backward counting) and posture. The first experiment included 30 normal subjects and the second experiment 20 normal subjects. In Experiment 1 postural sway and performance of the mental task were measured in a 2 x 2 dual-task design (with or without mental task and calf stimulation). In Experiment 2 a similar design was used, the only difference being that during trials without the mental task, subjects were instructed to focus on their balance and provide a rating of body sway. Results showed that balance perturbation led to decreased performance on the cognitive task in Experiment 1, but not in Experiment 2. The mental task led to less body sway, while focused attention attenuated the effect. In conclusion, control of body sway and cognitive functioning are to some extent related.